X-ray tube and x-ray inspection device

Abstract

To provide an X-ray tube that can be reduced in size and cost while suppressing instantaneous interruption, and an X-ray inspection device equipped with the same.SOLUTION: An X-ray tube includes: a vacuum vessel 11 whose interior forms a vacuum area Ar; a filament 22 that is provided with the vacuum vessel 11 and emits electrons; and a target 63 that is provided with an end portion 11b of the vacuum vessel 11 and emits X-rays by irradiation of electrons from the filament 22. A semi-closed space 66 is provided that surrounds a periphery of the target 63 and has a communication hole 68 through which electrons directed toward the target 63 can pass. An opening 74 for evacuating the inside of the vacuum vessel 11 is provided in an inner wall of the semi-closed space 66.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an X-ray tube and an X-ray inspection device. [Background technology]

[0002] For example, an X-ray inspection device used for inspecting articles is equipped with an X-ray tube as an X-ray source. The X-ray tube has a structure in which electrons emitted from a filament collide with a target inside a vacuum chamber, generating X-rays that are irradiated from a window.

[0003] Patent Document 1 shows an X-ray tube having a vacuum vessel consisting of a vacuum enclosure having a cylindrical wall portion capped at one end with a collar and at the other end with an anode assembly. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2015-525953 Summary of the Invention [Problem to be solved by the invention]

[0005] X-ray tubes are being increasingly miniaturized to reduce the space required for the X-ray inspection equipment and manufacturing costs. To prevent X-ray interruptions due to abnormal discharge, all electrons emitted from the filament must reach the target. However, electrons emitted from the filament tend to reach geometric polarization portions of surrounding structures that are at the same potential as the target. For example, in the X-ray tube described in Patent Document 1, if an opening, such as a connection or hole for a vacuum pipe, is formed in the anode assembly located at one end of the cylindrical wall, electrons may reach the geometric polarization portion formed by this opening, causing an X-ray interruption. For this reason, in X-ray tubes, necessary structural components, such as the opening for vacuum evacuation, must be located sufficiently far from the target, which limits the ability to reduce the diameter.

[0006] Therefore, an object of the present invention is to provide an X-ray tube that can be made smaller and less expensive while suppressing instantaneous interruptions, and an X-ray inspection apparatus equipped with the same. [Means for solving the problem]

[0007] The present invention comprises the following configurations. (1) a vacuum vessel whose interior is a vacuum region; a filament provided in the vacuum vessel and emitting electrons; a target provided at an end of the vacuum vessel and emitting X-rays when irradiated with electrons from the filament; and a semi-closed space is provided that surrounds the target and has a communication hole through which electrons traveling toward the target can pass; an opening for drawing a vacuum inside the vacuum container is provided on an inner wall of the semi-closed space; X-ray tube. (2) the X-ray tube described above, which irradiates X-rays onto the transported inspection object (W); an X-ray detector (82) for detecting X-rays transmitted through the object to be inspected; a signal processing unit (83) that inspects the object to be inspected based on image information obtained by the X-ray detector; X-ray inspection equipment. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an X-ray tube that can be made smaller and less expensive while suppressing momentary interruptions, and an X-ray inspection apparatus including the same. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a vertical cross-sectional view along the axial direction of an X-ray tube according to an embodiment. [Figure 2] FIG. 2 is a horizontal cross-sectional view along the axial direction of the X-ray tube according to the embodiment. [Figure 3] FIG. 3 is a perspective view of the X-ray tube with a part cut away. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a side view of the cathode structure of the X-ray tube. [Figure 7] FIG. 7 is a schematic diagram of an X-ray inspection device equipped with an X-ray tube. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Fig. 1 is a vertical cross-sectional view along the axial direction of an X-ray tube 10 according to an embodiment. Fig. 2 is a horizontal cross-sectional view along the axial direction of an X-ray tube 10 according to an embodiment. Fig. 3 is a perspective view with a part of the X-ray tube 10 broken away. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 1. Fig. 5 is a cross-sectional view taken along line VV in Fig. 1. Fig. 6 is a side view of a cathode structure 12 of the X-ray tube 10.

[0011] As shown in FIGS. 1 to 6, the X-ray tube 10 according to this embodiment has a vacuum vessel 11, a cathode structure 12, and an anode structure 13.

[0012] The vacuum vessel 11 is made of a metal material such as stainless steel, etc. The vacuum vessel 11 is formed in a cylindrical shape and has annular flange portions 14 and 15 that protrude inward at one end 11a and the other end 11b.

[0013] The cathode structure 12 is housed in a vacuum vessel 11. The cathode structure 12 is fixed to one end 11a of the vacuum vessel 11. The anode structure 13 is fixed to the other end 11b of the vacuum vessel 11. In the X-ray tube 10, the inside of the vacuum vessel 11, to which the cathode structure 12 and the anode structure 13 are fixed at both ends, is a vacuum region Av, and this vacuum region Av is evacuated.

[0014] The cathode structure 12 has a filament support 21, a filament 22, and a Wehnelt 23.

[0015] The filament support part 21 is made of ceramic and is formed in a generally bottomed cylindrical shape having a bottom 25. The filament support part 21 is housed in the vacuum vessel 11 with the bottom 25 facing the other end 11b of the vacuum vessel 11. The end of the filament support part 21 opposite the bottom 25 is airtightly joined and supported by a flange part 14 formed at one end 11a of the vacuum vessel 11 via a cylindrical support member 26 and an annular connecting member 27.

[0016] A pair of filament electrodes 31 and a pair of Wehnelt electrodes 32 are provided on the bottom 25 of the filament support part 21. These filament electrodes 31 and Wehnelt electrodes 32 are provided on the bottom 25 of the filament support part 21 so as to penetrate between the vacuum region Av and the outside, respectively.

[0017] The filament electrode 31 is made of a conductive metal material and has a fixed portion 35 and an electrode rod portion 36. The filament electrodes 31 are fixed at intervals so that the fixed portions 35 penetrate the bottom portion 25 of the filament support portion 21, and the electrode rod portions 36 protrude from the tip side of the filament support portion 21. Ends of filaments 22 made of wire material such as tungsten are connected to the tips of the electrode rod portions 36 of these filament electrodes 31, respectively. As a result, the filaments 22 are attached so as to span the tips of the electrode rod portions 36 of the filament electrodes 31.

[0018] The Wehnelt electrode 32 is made of a conductive metal material and has a fixed portion 41 and a support rod portion 42. The Wehnelt electrodes 32 are fixed at a distance from each other so that the fixed portion 41 penetrates the bottom portion 25 of the filament support portion 21, and the support rod portion 42 protrudes toward the tip side of the filament support portion 21. The Wehnelt electrode 32 has a screw hole (screw structure) 33 in its support rod portion 42.

[0019] The Wehnelt 23 is made of a conductive metal material. The Wehnelt 23 is formed in a cylindrical shape, and a mounting wall 51 that protrudes toward the inner periphery is formed in the axial middle of the Wehnelt 23. The mounting wall 51 has a pair of holes 52 and a pair of screw holes 53. The pair of holes 52 and the pair of screw holes 53 are located on opposite sides of the center. The screw holes 53 are located at different positions in the circumferential direction relative to the holes 52.

[0020] Flat head screws 54 are inserted into the holes 52 of the mounting wall 51, and these flat head screws 54 are screwed into the threaded holes 33 formed in the support rod 42 of the Wehnelt electrode 32. As a result, the Wehnelt electrode 23 is screwed to the Wehnelt electrode 32 and supported on the bottom 25 of the filament support part 21.

[0021] The Wehnelt 23 has a disk-shaped wall 55. The wall 55 is made of a conductive metal material. The wall 55 is attached to the mounting wall 51 of the Wehnelt 23 from the tip side of the Wehnelt 23. A slit 56 is formed in the wall 55. The filament 22 fixed to the electrode rod portion 36 of the filament electrode 31 is housed in the slit 56 of the wall 55. The filament 22 is arranged with a substantially uniform gap between the inner circumferential surface of the slit 56 and the outer circumferential side.

[0022] The wall 55 has a pair of holes 57. These holes 57 are arranged on both sides of the slit 56. Screws 58 are inserted into the holes 57 and screwed into the screw holes 53 formed in the mounting wall 51. In this way, the wall 55 is fixed to the mounting wall 51 by the screws.

[0023] The holes 57 formed in the wall body 55 have an inner diameter larger than the outer diameter of the screws 58 inserted into these holes 57. This allows the wall body 55 to be displaced relative to the mounting wall body 51 by the amount of the gap between the outer periphery of the screws 58 and the inner periphery of the screw holes 53 when the screws 58 are loosely screwed into the screw holes 53 of the mounting wall body 51 and temporarily fixed. Therefore, by adjusting the position of the wall body 55 relative to the mounting wall body 51 and mounting it, the wall body 55 can be positioned with a substantially uniform gap between the inner periphery of the slit 56 of the wall body 55 and the outer periphery of the filament 22.

[0024] The cathode structure 12 also has a molecular adsorption member 59. When a current is passed through the molecular adsorption member 59 and it is heated, it adsorbs the surrounding gas and increases the degree of vacuum in the vacuum region Av. The molecular adsorption member 59 has a pair of terminals 59a. One terminal 59a of the molecular adsorption member 59 is connected to the electrode rod portion 36 of one filament electrode 31, and the other terminal 59a is connected to the support rod portion 42 of one Wehnelt electrode 32.

[0025] The anode structure 13 includes an anode fixing member 61 , a target mounting member 62 , and a target 63 .

[0026] The anode fixing member 61 is formed of, for example, a metal material such as stainless steel, which is the same material as the vacuum vessel 11. The anode fixing member 61 has a flange portion 65, which is airtightly joined to a flange portion 15 formed on the other end 11b of the vacuum vessel 11.

[0027] A semi-closed space 66 is formed in the anode fixing member 61. The anode fixing member 61 also has a partition wall 67 on the side facing the vacuum region Av. The partition wall 67 has a communication hole 68 in its center that communicates with the semi-closed space 66. This allows the semi-closed space 66 to communicate with the vacuum region Av in the vacuum vessel 11 via the communication hole 68. The partition wall 67 has a smooth surface 67a on the side facing the vacuum region Av.

[0028] The semi-closed space 66 is composed of an axial space 66a extending in the axial direction of the X-ray tube 10 and a radial space 66b extending in the radial direction of the X-ray tube 10 so as to be perpendicular to the axial space 66a. The communication hole 68 is formed on one end side of the axial space 66a.

[0029] One end of the radial space 66b is open at the circumferential surface of the anode fixing member 61. The opening of this radial space 66b is a window 72 that is sealed by a transmission plate 71 made of, for example, beryllium. An opening 74 is formed at the other end of the radial space 66b, and a suction pipe 73 is connected to this opening 74.

[0030] The target mounting member 62 is made of a metal material that has electrical conductivity and excellent thermal conductivity, such as copper or a copper alloy. The target mounting member 62 has a mounting portion 75, a fitting portion 76, and a flange portion 77. The mounting portion 75 has an inclined end surface, and a plate-shaped target 63 is attached to this end surface. The target 63 is made of tungsten.

[0031] The target mounting member 62 has a fitting portion 76 that fits into a fitting hole 69 formed at the other end of the axial space 66a of the anode fixing member 61, and a flange portion 77 that is joined to the anode fixing member 61. In this way, the target mounting member 62 is fixed to the anode fixing member 61. With the target mounting member 62 fixed to the anode fixing member 61, the target 63 attached to the mounting portion 75 is placed at the end of the axial space 66a in the semi-closed space 66. The target 63 is placed in a state inclined at approximately 45 degrees toward the window portion 72 with respect to the axial direction of the X-ray tube 10.

[0032] In the X-ray tube 10, when evacuating the vacuum region Av, suction is performed through the suction pipe 73 connected to the anode fixing member 61 and communicating with the semi-closed space 66. Thereafter, power is supplied to the molecular adsorption member 59 through the filament electrode 31 and the Wehnelt electrode 32 to which the terminal 59a of the molecular adsorption member 59 is connected. This causes the molecular adsorption member 59 to adsorb the surrounding gas, thereby increasing the degree of vacuum in the vacuum region Av.

[0033] In the X-ray tube 10 configured in this manner, a voltage is applied to the filament 22 so that it serves as the cathode and the target 63 serves as the anode, and current is passed through the filament 22 via the filament electrode 31. Electrons are then emitted from the heated filament 22, narrowed and focused by the Wehnelt 23, and accelerated to collide with the target 63, which serves as the anode. X-rays are thus generated in the target 63, and these X-rays are irradiated to the outside through the window 72.

[0034] As described above, in the X-ray tube 10 according to this embodiment, the opening 74 for evacuating the vacuum vessel 11 is provided in the inner wall of the semi-closed space 66 that surrounds the target 63. Therefore, it is possible to eliminate the shape polarization portion that would otherwise be formed by providing the opening on the vacuum region Av side, and to suppress abnormal discharge caused by electrons reaching the shape polarization portion. Furthermore, it is possible to suppress an increase in size, which would be caused by providing the opening at a position away from the target 63 on the vacuum region Av side in order to suppress abnormal discharge. In other words, it is possible to suppress instantaneous interruption of X-rays due to abnormal discharge while reducing the size and cost.

[0035] Furthermore, a window 72 for transmitting X-rays emitted from the target 63 and irradiating them to the outside is provided on the inner wall of the semi-closed space 66 surrounding the periphery of the target 63. Therefore, the provision of the window 72 on the vacuum region Av side can eliminate a geometric polarization portion, suppressing abnormal discharge caused by electrons reaching the geometric polarization portion and suppressing instantaneous interruption of X-rays.

[0036] Furthermore, since the vacuum region Av and the semi-closed space 66 are separated by a partition 67 having a smooth surface on the side of the vacuum region Av, even if the inner wall of the semi-closed space 66 is uneven, electrons from the filament 22 can be smoothly guided to the target 63 through the communication hole 68 of the partition 67 while suppressing abnormal discharge.

[0037] Furthermore, by mounting the target 63 on the target mounting member 62 made of copper or a copper alloy, which has excellent thermal conductivity, the heat dissipation properties of the target 63 can be improved.

[0038] Next, an example of an X-ray inspection apparatus equipped with the X-ray tube 10 configured as described above will be described. FIG. 7 is a schematic diagram of an X-ray inspection apparatus 100 equipped with an X-ray tube 10. As shown in FIG. 7, the X-ray inspection apparatus 100 includes an X-ray tube 10, a transport unit 81, an X-ray detector 82, a signal processing unit 83, and a display unit 84, and is incorporated, for example, into a part of a transport line for an inspection object W. The X-ray inspection apparatus 100 includes the X-ray tube 10 having the above-described structure as an X-ray generator.

[0039] The transport unit 81 is a conveyor in which a loop-shaped transport belt 86 is wound around a plurality of transport rollers 85. The transport unit 81 sequentially transports the inspection objects W at intervals in the transport direction A by rotating the transport rollers 85 using a motor 87.

[0040] The X-ray tube 10 is disposed above the transport unit 81, and irradiates the inspection object W, which is transported in the transport direction A by the transport unit 81, with X-rays from above. The X-ray detector 82 detects the X-rays that have been emitted from the X-ray tube 10 and passed through the inspection object W, and outputs an X-ray detection signal, which is an electrical signal corresponding to the amount of transmitted X-rays. The signal processing unit 83 determines the quality of the inspection object W (presence or absence of foreign matter, presence or absence of defective sealing, etc.) based on the X-ray image of the inspection object W obtained from the X-ray detection signal of the X-ray detector 82. The display unit 84 is composed of various display devices, for example, a liquid crystal display, and displays the determination results of the signal processing unit 83 and the X-ray inspection image of the inspection object W.

[0041] Furthermore, the X-ray inspection device 100 equipped with the X-ray tube 10 is small and has reduced interruptions, so it is possible to improve inspection performance while saving space in the device and reducing equipment costs.

[0042] As such, the present invention is not limited to the above-described embodiments, and the present invention also contemplates the mutual combination of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the description in the specification and well-known techniques, and these modifications and applications are included in the scope of protection sought.

[0043] As described above, the present specification discloses the following: (1) a vacuum vessel whose interior is a vacuum region; a filament provided in the vacuum vessel and emitting electrons; a target provided at an end of the vacuum vessel and emitting X-rays when irradiated with electrons from the filament; and a semi-closed space is provided that surrounds the target and has a communication hole through which electrons traveling toward the target can pass; An X-ray tube, wherein an opening is provided in an inner wall of the semi-closed space for evacuating the inside of the vacuum vessel. In an X-ray tube with this configuration, an opening for evacuating the vacuum vessel is provided on the inner wall of the semi-closed space surrounding the target. Therefore, it is possible to eliminate the geometric polarization portion that would otherwise be created by providing an opening on the vacuum region side, and to suppress abnormal discharge caused by electrons reaching the geometric polarization portion. Furthermore, it is possible to suppress an increase in size, which would be caused by providing an opening on the vacuum region side away from the target in order to suppress abnormal discharge. In other words, it is possible to suppress instantaneous X-ray interruptions caused by abnormal discharge while reducing size and costs.

[0044] (2) The X-ray tube according to (1), wherein an inner wall of the semi-closed space is provided with a window portion that allows X-rays emitted from the target to pass through and be irradiated to the outside. In an X-ray tube with this configuration, a window is provided on the inner wall of the semi-closed space surrounding the target, allowing X-rays emitted from the target to pass through and irradiate the outside. This eliminates the geometric polarization portion that would otherwise be created by providing a window on the vacuum region side, suppressing abnormal discharge caused by electrons reaching the geometric polarization portion and preventing instantaneous X-ray interruptions.

[0045] (3) The X-ray tube according to (1) or (2), further comprising a partition wall between the vacuum region and the semi-closed space, the partition wall having a smooth surface on the vacuum region side, and the communication hole formed in the partition wall. In an X-ray tube with this configuration, the vacuum region and the semi-enclosed space are separated by a partition wall whose surface on the vacuum region side is smooth. Therefore, even if the inner wall of the semi-enclosed space is uneven, electrons from the filament can be smoothly guided to the target through the communicating hole in the partition wall while suppressing abnormal discharge.

[0046] (4) The X-ray tube according to any one of (1) to (3), wherein the target is attached to a target mounting member made of copper or a copper alloy. According to this X-ray tube, the target is attached to a target mounting member made of copper or a copper alloy, which has excellent thermal conductivity, thereby improving the heat dissipation properties of the target.

[0047] (5) An X-ray tube according to any one of (1) to (4) that irradiates an X-ray onto an object to be inspected (W) being transported; an X-ray detector (82) for detecting X-rays transmitted through the object to be inspected; a signal processing unit (83) that inspects the object to be inspected based on image information obtained by the X-ray detector; X-ray inspection equipment. According to the X-ray inspection apparatus having this configuration, since it is equipped with a small X-ray tube with reduced interruptions, it is possible to improve inspection performance while saving space for the apparatus and reducing equipment costs. [Explanation of symbols]

[0048] 10 X-ray tube 11 Vacuum container 22 filaments 62 Target mounting member 63 Target 66 Semi-enclosed space 67 Bulkhead 68 Communication hole 72 Window 74 Opening 100 X-ray inspection equipment Av vacuum area

Claims

1. a vacuum vessel (11) whose interior is a vacuum region (Av); a filament (22) provided in the vacuum vessel for emitting electrons; a target (63) provided at the end (11b) of the vacuum vessel and emitting X-rays when irradiated with electrons from the filament; and a semi-closed space (66) surrounding the target and having a communication hole (68) through which electrons toward the target can pass; An opening (74) for drawing a vacuum inside the vacuum container is provided on the inner wall of the semi-closed space. X-ray tube (10).

2. A window (72) is provided on the inner wall of the semi-closed space to allow X-rays emitted from the target to pass through and be irradiated to the outside.

10. The X-ray tube of claim 1.

3. Between the vacuum region and the semi-closed space, there is provided a partition wall (67) having a smooth surface on the vacuum region side, and the communication hole is formed in the partition wall.

10. The X-ray tube of claim 1.

4. The target is mounted on a target mounting member (62) made of copper or a copper alloy.

10. The X-ray tube of claim 1.

5. an X-ray tube according to any one of claims 1 to 4, which irradiates an X-ray toward an object to be inspected (W) being transported; an X-ray detector (82) for detecting X-rays transmitted through the object to be inspected; a signal processing unit (83) that inspects the object to be inspected based on image information obtained by the X-ray detector, An X-ray inspection device (100).

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